fix materialization of one bit constants and global values which are accessed through
a base GOT entry.

Summary:
get tip of tree mips fast-isel to pass test-suite

Two bugs were fixed:

1) one bit booleans were treated as 1 bit signed integers and so the literal '1' could become sign extended.
2) mips uses got for pic but in certain cases, as with string constants for example, many items can be referenced from the same got entry and this case was not handled properly.

Test Plan: test-suite

Reviewers: dsanders

Reviewed By: dsanders

Subscribers: mcrosier

Differential Revision: http://reviews.llvm.org/D4801

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215155 91177308-0d34-0410-b5e6-96231b3b80d8